Hydrocarbon polymers which contain reactive functional groups are known in the art. For example, Japanese (Kokai) 7-102017 to Kanegafuchi Chemical Industry discloses the preparation of various polymers having terminal unsaturation by reacting the corresponding hydroxyl-terminated polymer with a compound selected from an allyl halide, an acrylic acid, an oxirane ring-containing compound having carbon-carbon double bonds or a compound containing an isocyanate group and carbon-carbon double bonds in its molecule. The starting polymer, which must contain at least 1.1 hydroxyl groups per molecule, can be prepared by carrying out a chain scission of the hydrocarbon polymer chain by reacting it with ozone, followed by reduction with lithium aluminum hydride. This method for producing the hydroxy-functional precursor polymer has a disadvantage in that the chain scission results in a reduction of polymer molecular weight, as observed in Reference Example 1 of the above mentioned Kanegafuchi publication.
Further, polyisobutylenes and polybutylenes which have 2-methyl-1-propenyl end groups of the formula --HC.dbd.C(CH.sub.3).sub.2 are available commercially. However, this type of unsaturation exhibits poor reactivity with SiH-functional silanes and siloxanes. A lack of reactivity is also observed in attempts at copolymerization with other olefin-based systems such as polyacrylics and polystyrenics. Additionally, these unreactive olefinic polyisobutylenes can not effectively be used to modify systems cured by conventional free radical means such as ultraviolet (u.v.) light and peroxides.
There is, therefore, a need for easily prepared polyisobutylene polymers and oligomers which contain unsaturated groups having improved reactivity with SiH-functional compound, better reactivity with olefin-based polymerization systems and which exhibit an improved efficiency with respect to free radical cure mechanisms, as desirable in such applications as protective coatings.